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Red Bumps on Dogs’ Skin: 5 Reasons Why It Happens

Red bumps on dogs’ skin can appear for harmless reasons (hives, warts, or skin tags) and harmful reasons. The harmful red bumps appear due to cancer or some types of benign tumors that can become malignant. Do not panic if your dog develops red bumps, but take it to the vet for a proper examination and diagnosis.

Finding a bump or lump on your dog’s skin can cause worry and panic. But you have to remember that not every swelling or growth is dangerous. 

Even if it is cancer, it’s important to go to the vet before panicking. The veterinarian will examine your dog and help your four-legged friend.

In order to detect cancer or any other skin diseases in time, it is important to check your dog regularly. Take it to the vet if a suspicious growth or swelling appears on its skin.

Bumps and lumps can appear anywhere on the dog’s body: the face, legs, stomach, between the toes, back, tail, etc. In most cases, red bumps on dogs’ skin are benign (meaning they are not cancerous).

Why Does My Dog Have Red Bumps on Its Body?

Red bumps on dogs’ skin can be skin tags, warts, insect bites, blisters, benign tumors, or cancer. In most cases, they are benign growths and are not cause for concern. Red bumps can appear at any age, but older dogs are generally more prone. Contact the vet if your dog develops red bumps on its skin.

Red bumps on dogs’ skin can be of different sizes and shapes, depending on the cause. They can occur at any age and in any breed, but it seems older dogs and some breeds are more prone to developing them.

Here are the most common causes of why bumps on dogs’ skin develop:

  • Benign tumors
  • Malignant tumors
  • Hives
  • Skin tags
  • Warts
Why Does My Dog Have Red Bumps on Its Body

1. Benign Tumors

Benign tumors are non-cancerous skin growths. In some cases, they can become cancerous, endangering your dog’s life. They can occur anywhere on the body, both in hairy and hairless areas.

Tumors affecting the skin are common in dogs. Of these, 60-80% are benign, i.e. non-cancerous (harmless) tumors.

In some cases, these harmless tumors can become malignant and harmful. It is recommended to have the vet examine any bumps you detect on your dog’s skin.

Many skin tumors can be treated through early surgical removal. 

If an abnormal growth is removed from your dog’s skin, it should be examined by a veterinary pathologist (i.e. sent to a lab for diagnosis). In case the growth is cancerous, further treatment is needed.

Here are the most common types of benign skin tumors that cause red bumps in dogs:

  • Histiocytoma
  • Mastocytoma
  • Hemangioma
Benign Tumors on dog
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Histiocytoma is a benign tumor that does not pose a risk to your dog’s health. They can appear in any region of the body but especially develop on the head.

It can occur in dogs of any age but is more commonly diagnosed in dogs under the age of three years. Histiocytoma is one of the most common tumors in this age group.

The breed or sex of dogs does not seem to influence the development of the disease, but Boxers and Bull Terriers are more prone to it.[1]

These tumors appear quickly and are small, red, round, and hairless. They will often ulcerate, then become smaller and disappear. 

Histiocytomas usually appear as a solitary mass, but more than one can be present at once.


Mastocytoma is a benign tumor that has unpredictable behavior and increased malignancy. The main form of mastocytoma in dogs is cutaneous or subcutaneous.[2]  Visceral or systemic forms are also found.

Canine cutaneous mastocytoma represents 16-21% of skin tumors in dogs.

Some breeds are predisposed to mastocytomas:

  • Boxer
  • Boston terrier
  • Bull terrier
  • Bullmastiff
  • English bulldog
  • Pug
  • Labrador retriever
  • Golden retriever
  • Beagle
  • Schnauzer
  • Shar-Pei
  • Rhodesian Ridgeback
  • Weimaraners

In the cutaneous form, one or more tumors occur on the surface of the body. Masotcytomas can appear “overnight” or they can grow over the course of a few months or years.

These tumors appear as bumps on the skin surface (usually in places without hair). They can be single or multiple and have an elastic consistency.

Mastocytomas usually have a diameter of 1-4 cm (~0.4-1.5 inches) and are located on the skin or at the border between the skin and mucous membranes. They can appear all over the body but they are most often found on the legs.

They can cause itching and ulceration because dogs groom themselves excessively.

Cutaneous Hemangioma

Hemangiomas are benign vascular tumors of the skin. They appear as a firm, raised lump anywhere on or under the skin.[3]

Most of the time, hemangiomas are red growths that resemble a blood blister. In other cases, they can be the same color as the skin or turn blue/purple because of the blood inside.

Hemangiomas can ulcerate, causing bleeding. If they appear under the axilla or in the groin area, they can cause pain and discomfort when dogs are moving.

Sebaceous Adenoma

Sebaceous adenomas are benign tumors of the sebaceous glands in the skin.[4] They are up to one centimeter in diameter, white-pink, and have irregular edges. 

These sebaceous adenomas can secrete a white, greasy substance.

Sebaceous adenomas do usually not cause health problems unless they become infected. Infection of sebaceous adenomas can occur as a result of trauma to the tumor (rupture, biting, scratching).

2. Malignant Tumors

Malignant tumors are harmful tumors that metastasize to other organs and cause death. Their symptoms are usually severe and are not limited to the appearance of red bumps on the skin. Symptoms can also include local bleeding, pain, weight loss, or other symptoms.

Malignant skin tumors are not as common in dogs as benign tumors.

These tumors grow quickly and spread to other parts of the body (metastasis). They can damage the organs and their functions, which usually leads to the death of the affected dog.

Here are the most common forms of malignant skin tumors in dogs that manifest through red bumps:

  • Hemangiosarcoma
  • Squamous cell carcinoma
Malignant Tumors

Cutaneous Hemangiosarcoma

Cutaneous hemangiosarcoma occurs most often in middle-aged or older dogs, but the disease has also been diagnosed in dogs younger than three years old. 

Hemangiosarcoma is characterized by the appearance of single or multiple red or pink masses (bumps or growths) on dogs’ skin. These can ulcerate and cause bleeding and pain.

Some breeds are more predisposed to these tumors:

  • German shepherd
  • The Golden retriever
  • Labrador retriever

Males are more prone than females. Large and giant dogs are also more affected than small and toy dogs.

Prolonged exposure to sun and UV radiation are two factors that favor the appearance of cutaneous hemangiosarcomas.[5]

Squamous Cell Carcinoma

Squamous cell carcinoma usually occurs in hairless areas and is caused by prolonged sun exposure.

The bumps or growths that occur can have various colors, including red, white, or gray. They can ulcerate and cause pain and bleeding.

This cancer is aggressive, but it metastasizes slowly.

3. Hives

Hives on dogs
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Hives appear in the form of small red bumps in different parts or on the entire surface of the body, depending on the cause.

Hives or urticaria (the medical term) is a skin rash that can appear for many reasons:

  • Contact with an allergen
  • Contact with an irritating substance or plant
  • Insect bites

They look like small round or oval, red, raised, itchy bumps on the skin.

It usually resolves on its own in mild cases. In severe cases, the veterinarian can prescribe local or oral treatments with antihistamine (antiallergic) drugs or steroids.

4. Skin tags

Skin tags on dogs
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Red skin tags appear with age and are harmless. They usually appear in the groin and axillary area where the skin rubs against itself.

The excessive growth of connective tissue of the skin leads to the appearance of skin tags. They can appear in any breed with old age. 

The most common areas of occurrence are those where dogs’ skin rubs against itself the most:

  • Axillary
  • Groin area

5. Warts

dog Warts
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Warts or papillomas are caused by papillomaviruses. They are harmless benign tumors that usually resolve on their own. In some cases, they may need to be removed through surgery.

Warts are caused by DNA papillomaviruses. These have an incubation period of 1-2 months. Papillomas are contagious and can be transmitted to other dogs.

Papillomas are cauliflower-shaped growths, irregular, pedicled, pink, white, or gray in color. They usually heal on their own within a few months of their formation. In some cases, surgery may be needed to remove them.

Related: Red Bumps on Dogs’ Paw

About Iulia Mihai (DVM)

Dr. Iulia is a certified veterinarian with more than 10 years of experience in the field. With extensive knowledge of diet, care, and medication, she helps Misfit Animals provide readers with accurate knowledge on technical topics.

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